1 / 12

Models for MPEG2 and Video Conferencing

Explore MPEG-2 parameters, video conferencing modes, coding techniques, bit-rates, packet sizes, and standards for efficient communication.

finch
Download Presentation

Models for MPEG2 and Video Conferencing

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Models for MPEG2 and Video Conferencing Sachin Deshpande Srinivas Kandala Sharp Laboratories of America, Inc. Camas, WA 98607 S. Deshpande, S. Kandala, Sharp

  2. MPEG 2 VBR Source Model Scene 1 Scene 2 Scene Length= N*d frames • GOP = Group of Pictures • Frame rate = 30 frames/sec • d is geometrically distributed • I frames are log-normally distributed • i.i.d or AR process • B & P frames are iid log-normal GOP d GOP 1 GOP 2 I B B P B B P B B P B B P B B I N Frames (typically N=15 or 12) S. Deshpande, S. Kandala, Sharp

  3. MPEG 2 Parameters S. Deshpande, S. Kandala, Sharp

  4. Video Conferencing Parameters • Video-conferencing typically use H.263 or H.261 standards for video coding. • CBR is usually employed, by the application using a rate control algorithms. In certain situations frames may be dropped to meet the target bit-rate. Typically no B frames are used due to low latency requirement. • Packet size - typically can be 576 bytes/ 1000 bytes/ 1500 bytes for Internet. • -Usage of smaller packet size (576 bytes) is more conservative since there is a less chance of getting fragmented. • -Latency is not an issue for high rates even if we use 1500 bytes. S. Deshpande, S. Kandala, Sharp

  5. Appendix: A Brief tutorial on Video Conferencing Standards S. Deshpande, S. Kandala, Sharp

  6. Introduction • H.320,321,322,323,324 – Umbrella standards for multimedia communications (video conferencing) • H.323: multimedia communication over packet switched networks that do not provide a guaranteed QoS • H.261, H.263(+) : video coding standards used with H.323 • G.711, G.722, G.723, G.728, G.729 : audio coding standards used with H.323 S. Deshpande, S. Kandala, Sharp

  7. Video Conferencing Modes • Point-to-point / Multi-point conference • Multipoint conference: • Centralized Multipoint control unit (MCU) • Distributed multipoint • Unicast / Multicast S. Deshpande, S. Kandala, Sharp

  8. Video Coding for Video Conferencing • Interactive nature: • Stringent requirements on latency (150-400 ms) • No B frames • QCIF (176x144), CIF (352x288) typical frame resolutions (also possible : SQCIF, 4CIF, 16CIF) • Frame rates : 5 to 30 frames per second S. Deshpande, S. Kandala, Sharp

  9. Video Coding for Video Conferencing • Bit-rates (including audio): mostly CBR geared towards different client speeds • < 56 Kbps (modem) (typically use H.263 at 5-15 fps, G.723 at 5.3/6.3 Kbps) • < 128 Kbps (ISDN) (typically use H.263 at 10-20 fps, G.723 at 5.3/6.3 Kbps) • (256 Kbps-1.5 Mbps) Higher bitrate (DSL, cable modem, T1) S. Deshpande, S. Kandala, Sharp

  10. Video Coding for Video Conferencing • Packet sizes : • RTP payload for H.261, H.263, H.263+ • Group of blocks (GOB) based packetization • Typically for Internet environment packet size can vary from 200-1500 bytes • Overhead of 40 bytes header (RTP+UDP+IP) per packet, so keeping packet size close to maximum transfer unit (MTU) of network desirable (taking into account latency requirement) S. Deshpande, S. Kandala, Sharp

  11. H.261, H.263 (+) • H.261 : • P x 64 Kbps (P=1,2,3...30) • Older standard, H.263(+) outperforms it • H.263(+) : • H.263 : baseline standard, 4 optional annexes • H.263+ : baseline standard, 16 optional annexes S. Deshpande, S. Kandala, Sharp

  12. Sample References for Video Conference Traffic Models • Heyman D., Tabatabai A., Lakshman T.V., “Statistical analysis and simulation study of video teleconference traffic in ATM networks,” IEEE J Sel. Areas in Comm, 2(1), pp. 49-59, 1992. • Yegenoglu F., Jabbari B., Zhang Y.Q., “Motion-classified autoregressive modeling of variable bit-rate video,” IEEE Trans. CSVT, 3(1), pp. 42-53, 1993. • Reibman A., Berger A.W., “Traffic descriptors for VBR video teleconferencing,” IEEE/ACM Trans. Networking, 3, pp 329-339, 1995. S. Deshpande, S. Kandala, Sharp

More Related